Those who gamble for fun anyway have their limits. They cant change goal again and again. There will be a moment when greed factor comes into play. No matter how they convince themselves that they gamble for fun and money is just a paper, they will face a moment when they will consider pity to lose such an amount.
Even if they have no certain limit, they probably use small money only. No one gamble for fun who force using big money. People who tend to use big amount of money because they want to try achieving big prizes. They may use small money at beginning, but it is getting bigger gradually when they are trying to win bigger prizes. Meanwhile for people who gamble for fun, I think they won't be greedy because they are aware of the bad impacts. People actually prefer to gamble for fun because they want to avoid of an excessive gambling. 